Installation guide

Connecting Additional Devices to Your System
Connecting Additional Devices to Your System
Bus Expansion
Ports
A bus expansion port on the front of most mass storage
compartments enables you to extend the bus that runs through
that compartment outside the system. As a result, you can
connect external mass storage devices, either standalone devices
or devices in an expander, such as the R400X, to the buses inside
your system. Note, however, that you can only connect DSSI
devices to a DSSI bus and only SCSI devices to a SCSI bus.
Figure 6–4 shows the location of the bus expansion ports on the
DEC 4000 AXP system.
Extending a
Fast SCSI Bus
Buses that run fast SCSI cannot be extended outside the system.
If you wish to extend a SCSI bus that is currently running fast
SCSI, you must reconfigure the hardware in that compartment.
Contact your Digital service representative.
Connecting
Additional
Devices: Rules
Each DEC 4000 AXP mass storage compartment can hold up
to four devices. However, each bus can support up to seven
mass storage devices. This means that you can connect three,
and possibly more, external drives to a bus that supports a
compartment.
For instance:
• If a compartment holds four drives, you can connect three
external drives to the bus that supports that compartment.
• If a compartment holds one drive, you can connect six
external drives to the bus that supports that compartment.
6–18 System Configuration